package com.bit.java;

import java.util.Scanner;

public class Test7 {
    public static int jump(int n) {
        if(n <= 3) {
            return n;
        }
        return jump(n - 1) + jump(n - 2);
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int ret = jump(n);
        System.out.println(n);
    }


}
